Effect of confinement and Coulomb interactions on the electronic structure of (111) LaAlO$_3$/SrTiO$_3$ interface

TL;DR

This study models the electronic structure of the (111) LaAlO₃/SrTiO₃ interface using a tight-binding supercell approach, incorporating confinement, band bending, and Hubbard interactions, and compares results with experimental data.

Contribution

It introduces a comprehensive self-consistent calculation including Hubbard interactions for the interface's electronic structure, aligning well with experimental observations.

Findings

Electronic sub-bands and Fermi surfaces match ARPES data.

Hubbard interactions do not deplete the 2D electron gas.

Interactions enhance electron density between layers and bulk.

Abstract

A tight binding supercell approach is used for the calculation of the electronic structure of the (111) LaAlO$_3$/SrTiO$_3$ interface. The confinement potential at the interface is evaluated solving a discrete Poisson equation by means of an iterative method. In addition to the effect of the confinement, local Hubbard electron-electron terms are included at mean-field level within a fully self-consistent procedure. The calculation carefully describes how the two-dimensional electron gas arises from the quantum confinement of electrons near the interface due to band bending potential. The resulting electronic sub-bands and Fermi surfaces show full agreement with the electronic structure determined by angle-resolved photoelectron spectroscopy experiments. In particular, it is analyzed how the effect of local Hubbard interactions changes the density distribution over the layers from the interface to the bulk. Interestingly, the two-dimensional electron gas at interface is not depleted by local Hubbard interactions which indeed induce an enhancement of the electron density between the first layers and the bulk.